Perforator gun with improved projectile restraining means



May 23, 1944- l vl. J.. MccuLLouGH 2,349,666

PERFORATOR GUN WITH IMPROVED PROJECTILE RESTRAINING MEANS Filed Feb. l0, 1940 @sienten Mey @3; infie Mention llehrnnry il@ molens.

itiiy present invention teintes to moons for pera foretine casing and relate, in 4particulier to n een for shooting projectiies through the Well oi. e. ces-ine set in a well, such employing my nevi enel improved method and ineens for delaying in ,Y itiei movement of the projectile, and wherein economy of gun manufacture, economy of up troep, end superior perforation results are obteineel.

fit is en object of the present invention to pro vvide n perforating gun wherein o. greater length of een 4here and greater velocity of projectile are obtained Vin a gun of a given diemeter, es com= pared to guns which have been previously empioyed for this purpose. lin :nony instances the production of a. well is corrieri to the surface of li-Cip i i no. tierces t@ intimes) the ground through an oil tube consisting of a Y string of pipe of much smaller diameter than the well casing ordinarily employed. I iindthat one of the results obtainable in' the use oi my present invention is the reduction of the overall diameter of an effective perioreting gun to such size im: the gun may be lowered through an oil tube which has been set in a vieil to the position ot which itis desired to perforete the casing, there, evolding the necessity of pulling the oil tube from the well.

1t is a further object oi' the invention to provide o. gun which is relatively cheap, or of low cost of manufacture, wherein economy of manufacturc, upkeep, and operating costs are maintained vilt-inuitv sacrice of e'iciency of operation, and in toot enabling a greater efficiency of operation then is obtainable from nieny of the previous types of perforating guns of comparatively high manufacture. upkeep, end operation costs.

l A further object of the invention is to provide a, perioreting gun having n simplified form ci projectile delaying means, whereby the invention avoids the use of the previously employed relotive expensive projectile delaying means. For cxample, to hold the bullet stationary for a time after ignition or the firing charge in the powder 'chamber of the previous types of gun lso as to build up the propelling ges pressure before release and discharge of theprojectilo, it has been In my present lndue to the use of a simpiiiied form o means for deleyinginitiel movement of the projectiietli om enabled to employ a projectile of simple cylindric iormfwithoutproiecting flanges or collars o high morele .veioeity is ohtiiined siccor= instr eicient penetrotion ci the ces-ing is ac completi.

it is on obiect oi the invention to provisie means in perioretins' een ier riolering the initie-l move= ment oi e proiectne'tlispcsed in the een isere, by retorriing the building; up of propelling easpres= sure edjeoent the rei-tr enti ieee of the projectile imnieziietely ritter ignition oi e tiring cheres in the @ring chore@ chamber associated with the gun bore, so thet the proiectiie will he discharged under force or e. lerne volonte of propelling ges et .en eectively hielt pressure.

it is en object ot the invention to provide o periorntine gun bovine e troll in such spaced reietion to the rear of the projectile disposed in the sun bore, thet the building up of a propeiling ses pressure adjacent the rear fece of the projectile is retarded sind en eiective elsy of the movement ofthe projectile is thereby obtained.

A further object is to provide e sun and pro c iectlie assembly wherein the gun here is so placed and -topuse such projectile in such mein'ier that-55 relative to other Wells of the gun that e, pro iectile in such gun bore hes o side well exposed to the initial gas pressure obtained from the burning of e. iirlne cheree in the firing charge chamber of the gun, end whereby an eiective delay of the movement of the projectile is ein tained.

Further objects and advantages of the inven tion will be brought out in the following part of the specicetion.

Referring to the drooling which is for illustretive purposes only:

Fig. l is e. view, sectioned on e. vertical plone of e embodying e preferred form of the inventlon. I

Fig. 2 is e fragmentary sectional view showing an alternative form of the projectile delay means es yeppiiecl te a multiple firing arrangement.

Fig. 3 is e. fragmentary sectional view showing en alternative form of projectile delay or re- ,streg means.

Fig. t is e, fragmentary section showing the rear end of o gun bore with the bullet removed therefrom.

Fig. 5 is en enlarged iregmentery section similor to Fie. fi to show a spaceedjacent the rear end of the bullet. i

in Fie` l I show e gun body it comprising a. suspension member i l and e plurality of gun body sections i2 and iii secured togetherinexial relation by threaded joints i5 individually identified es io, leb, and i ic. The top or suspension member ii `carries ,a @ring pin l in an axial opening Il, to engage, when driven down, a priming element I8 comprising a cartridge carried in a removable cylindrical block I9 seated in a counterbore 20 in a position above an ignition charge chamber 2|. The joint |5a between the suspension member II and the body section 'I2 comprises a threaded pin 22 which extends down from the suspension member II into a threaded box 23. The primer block I9 is disposed in the counterbore 20 which extends down from the bottom off the threaded box 23 so that when the joint |a is unscrewed. the block I9 may be removed, thereby exposing the iiring charge chamber 2| for the placing of an ignition charge 24 therein', and at which time a new primer I8 may be placed in the block ISI.v From the ignition charge chamber 2| a passage of small diameter 26 extends -down through a replaceable restraining member 39, threaded in the pin 21 of the joint |5b, tocommunicate with a firing charge chamber 28 projecting downward in they body section I3 from the-bottom of the threaded box 23 of the joint I5b, thus being in such position that unscrewing of this joint I5b will expose the chamber 28 for recharging, as by placing therein a chargeof powder 30 constituting the ring charge. .i

`I'rom one side of the body I3 an opening extends inward so as to form a gun bore 3|. The ring charge chamber 28 communicates with the inner end of the gun bore 3| through a passage 33 of such large diameter that the gas from the burning of the charge 30 may readily pass therethrough. It will be noted that the ring charge chamber 28 lies to one sideof the gun bore 3| so that the inner end of the gun bore 3| can be disposed relatively near to the external face of the body section I3 opposite from the external mouth of the gun bore 3|. Accordingly, the rear end face 34 of a projectile 35 placed. in the gun bore 3| as shown. will lie at a distance from the mouth 36 of the gun bore 3| considerably greater than the radial dimension of the gun body. In view of this, itis possible to keep the projectile under direct pressure of propelling gases while, it is traveling through a considerable distance asy compared to the diameter 4of the gun body, thereby obtaining a high muzzle velocity for a gun having a given body diameter.

From the'inner end portion of the gun bore 3| a passage 31 extends downward to the lower end face of the 4pin 40 forming the jointv |5c by which consecutive sections I3 are joined, this passage 31 having a threaded portion 38 to receive a restraining means 39 of replaceable type having a small diameter passage 39a therethrough communicating Iwith a succeeding flring charge' chamber 28 formed in the succeeding gun body section I3 which is substantially a duplicate of the section I3 .described in detail, with the exception that the gun bore 3| therein is faced in another direction from that of the gun bore in the upper section I3. Sealing means are provided' to prevent entry of water 4into the interior of the gun body, such sealing means including packing 48 around thev firing pin I6 and sealing members 58 placed in the gun bores 3| and 45 adjacent the outer ends of the projectiles 35 and'46. The sealing means 50 may consist of rubber cups which areforced into the` gun bores into the position shown or may consist of a sealing material placed in position and allowed to harden therein. .The packing 49 is forced into sealing engagement with v the ilring pin I6 by threaded plugs 52 which are screwed into diametrally disposed threaded openings 53.

As hereinbefore indicated a principle of my invention consists inl delaying the initial movement of the projectile from the gun body without the use on the bullet of shoulders, flanges or plates which by the shearing or deforming strength thereof delay the movement of projectilesl until the propelling gas pressure has built up to a desired extent. It will be noted that the projectile 35 is essentially cylindrical and may be readily machined from suitable material such as steel.' In the form of the invention shown in gun' body section'l3, a wall 54 is provided in a position adjacent to,k and in some instances in 4 mitted through the passage 2B to the chamber 28 to ignite the ring charge 38. The propelling gases resulting from the ignition of the charge 38 are` transmitted through the communicating passage 33 to the Ainner end'of the upper gun bore 3|, and the pressure" of these propelling gases rapidly builds up as the burning of the charge 38 progresses, but owing to the fact that `the inner end face'34 of the projectile 35 is spaced relatively close to the wall 54 the building up of gas pressure adjacent this rear end face 34 will be retarded, and by the time suicient pressure has built up adjacent the inner end face 34 to start outward movement of the projectile 35a very high gas pressure will have vbeen built upv in the chamber 28, the-passage 33 and the space 32 so that y .the time it reaches the muzzle or mouthr36 of the gun bore 3|. g

In the upper section I3 of Fig. 1 and in Fig. 4 I have indicated that the wall 54 may be cupped so that the peripheral portion 55 thereof may extend around an annular area of the side wall ci' the projectile 35. In Fig. 5, drawn to enlarged scale, I have shown a space 54 between the rear end of the bullet 35 and the wall 54 in which gas pressure may accumulate.Y It will be understood that this space 54' may be much less than a thousandth of an inch, and that it may consist of such space as exists when there is actual conl tact between the rearend face 34 of the bullet 35 and the wall 54, for the reason that in ordinary manufacturing processes the surfaces are notfso perfectlyformed that all portions of the walls-54 and 34 are in contact. -It will be understood, however, that the wall which lies .adjacent the rear end of a projectile may be flat and in i'act may-be spaced from the rear end face of the projectile, under which'circumstances a space.

of restricted volume will be formed adjacent the rear end face of the projectile in which the building up of propelling gas pressure is retarded. vAs an example, I have in body section I4 of Fig. 2 shown that the at wall lying adjacent the inner end face of avprojectile 45 'may comprise the in.- ner end face of another projectile.. It will be perceived, accordingly, that the rear end face 41 of each projectile 43 will serve as a means for ascenso retardingthe building up of pressure adjacent the rearend face of the other projectile. .Inria 2 I have lshown the existence of a space il between the rear end faces ti of the bullets te, and it will be understood that this spacemay vary within reasonably large limits and that it may be such space as exists when there is actual contact between the rear end faces El.

Fig. 2 shows a ilrlug charge chamber di which communicates through a passage ti `with substantially the center of a diametral bore et which forms a pair of gun bores et extending inward from the/exterior of the gun body i3 and communicating with the passage In each of these gun bores 5 there is a projectile Pit, these pro- Y Jectiles 6u being' positioned sothat the innerV end faces El thereof lie in such spaced relation, or in general practice substantially in engagement,

that the Space between the inner end faces @l wlll be of such size that the desired retarding enect will beattaned. A tiring charge de is placed in the tiring` charge chamber el. The propelling gas produced from theburning'of the char-gade will pass throughthe passage de, and owing to the relative closeness of the rear end faces di of the projectiles to ,there will be a short cielv in the building up of gas pressure against the rear end faces di, during which time a heavy pressure of gas accumulates in the chamber :il and the space, 43 so that when outward movement of the projectiles te nally starts, these projectiles will be moved through the respective gun bores $5 by propelling gas capable of producing in the projectiles a high muzzle velocity.

In Figs. l and 2 I have shown forms of mv invention wherein a part of the rear end of abuilet projecting into a gas space is covered, thereby the powder charge is setofi and increases to full' size as the projectile moves outward, .thereby permitting application to the rear end of the projectile the full pressure of the gases accumulated during the short time the initial movement of the projectile is retarded. Y Such mouth may be the mouth 83, shown in Fig. 3. One wall of this mouth is formed by the rear end of the projectile 3d, and

therefore its size may be decreased to nearly zero value by, ymoving the projectile 84 rightward from.

. the position in which it is shown. The mouth accomplishing a delay .in the forces which tend to hold it stationary, including inertia of the projectile and frictional resistance of the projectile `and the sealing means associated therewith.`

In Fig. 3 I show an alternative form of the invention wherein the covered portion of the inner end of the projectile consists of 1a side face of thc inner end of the projectile instead of the inner end face thereof.` l Y In this'viesir a gun body .section it' is shown having a @ring charge `chamber tu, a gun bore il l, and a passage di? connecting the chamber t@ with a side portion of the `inner end of the gun bore di. It will be noted that the interconnecting passage has a mouth d@ which leads into the side `e'all o' the bore lil. l projectile Elfi ol simple cylirniric form is placed in the gun bore @i in auch position that the inner end portion di thereof projects part way across the mouth il?. of the passage i3d. Accordingly, the upper face iii of this inner endportion of the projectile et' bb of the projectile dit. forcng the rearward por-iN tion of the projectiledownward tightly against the lower wall of the gun bore di so as to bind the projectile d@ stationary until suhi'cient pres-n surehas huilt up against the rear end face there of to startl its outward movement inthe gun bore. v In the use of the perfonitinaf assembly, shown in When a rins char'fe 'is' '35 and the peripheral wal1155, through which gas pressure may enter the space 5d adjacent the rear face of the projectile. A further important feature of my present invention consists in the provision in a gun of this character of'a chamber or space for the accumu- -lation of 'propelling gases under high pressure,

making* it possible to use a heavy charge of explosive as compared to the strength of the walls of the gun body. as a result of the cushioning effect of the chamber or space, and as the iinal result accomplishing a `higher muzzle velocity of the projectile by reason of the application of high' pressure propelling gases against the rear enel face of the projectile until it reaches and leaves the muzzle of the gun bore.

" ro the projectile te in the gun here, whereby to hold" It has'been the previous practice to design the iiring charge or powder chambers of guns of this type with relation to the quantity of powder required to propel the projectile and the strength of the chamber wall obtainable in a gun of a given diameter. `Where attempts havebeen made to increase the strength or` quantity of an eilplosive charge without increasing the diameter of the gun body, destruction of the gun body has resulted, or the gun barrels which are held in threaded openings have been blown out `of the gun body. `I nd that I am able to increase the muzzle velocity for a given diameter of gun very materially by providing an accumulator for gases under high pressure"prior to the discharge of the projectile. This accumulator may comprise a chamber formed in communication with the inner end of the gun here, or :'nits simplest form may consist merely of an. enlargement of the' firing charge chamber 'so that the volume oi the ilring charge chamber will be greater than the volume of the powderI charge, to an extent pron viding in the chamber a space which `will serve.

as a cushion for the detonation resulting from the burning of the powder charge and forholding a Volume of gas under high pressure which has i resultedV from the burning of Vthe powder charge.

Accordingly, the destructive effects of the detiene tion of the powder charge on the gun body or on me. 3. the fact that the projectile sa is usually `cramped in the inner end portion of the bore et Lthreaded joints oi the gun( structure is avoided.

and the provision of the gas accumulator or reservoir, in conjunction with the initial delayioi the projectile, enables the attainingj'of a high muzzle velocity of the projectile, for'the reason that .the propelling gases, under highpressure, are fed from the accumulator space of the gun body into the rear end of the gun bore as the projectile moves outward, maintaining an eil'ective propelling force against the rear end face of the projectile not only during the initial movement of the projectile but as the projectile moves through the outer portion of the gun bore.- It

will be perceived vaccordingly that the iiring` charge chambers 28 and 4| are given a volume materially larger than the volume oi' the body oi explosive material constituting the charges 30 and 48. In the prior practice the volume of the ilring charge chamber was completelyillledby the volume of the firing charge. This, of course, can be varied within working limits, depending upon the characteristics and burning speed of the explosive materials, and other factors including strength of steel employed in the gun body. size,

and inertia of projectile, length of gun bore, etc.I

scribed,y the combination of: a projectile; a gun` barrel to receive said projectile at the inner end thereof and to guide the same through its outward travel; means connected to the inner end of said barrel to supply propelling gases thereto; and wall means cooperating with the rear portion of said projectile so as to form a chamber adjacent the rear end face of said projectile,

saidchamber having an entrance opening for iiow of propelling gas into said chamber, said entrance opening transecting said chamber in advance of its rear end wall being of such small size as to retard the building up of gas pressure in said chamber, and the walls of said entrance opening being formed in part by the rear end of said projectile so that as said projectile moves outward the size of said entrance opening will increase.

2. In a perforating means of the character described, the combination of a projectile; a gun barrel to receive said projectile at the inner end thereof and to guide the same through its outward travel; means connected to the inner end of said barrel to apply propelling gas thereto, said means comprising walls forming a chamber communicating with said barrel; and wall means disposed in adjacent relation to the rear portion of said projectile to retard the building up of gas pressure adjacent the rear end face of said projectile to delay movement of said projectile while pressure builds up in said chamber.

3. In a perforating means oi' the character de'- scribed, the combination of: a projectile; a gun barrel to receive said projectile at the inner end thereof and to guide the same through its outward travel; means connected to the inner end of said barrel to apply propelling gas thereto, said means comprising walls forming a chamber communicating with said barrel; and a wall disposed in such relationjto the inner end of said projectile las-to retard the building up of pressure adjacent f the rear end face oi' said projectile to delay movef ment oi said projectile-while pressure builds up in said chamber. l

, 4. Inf a perforating means of the character described, the 'combination of: a body having a gun bore; means for applying propelling gas presf sure to the inner end of said gun bore, said means comprising a ring charge chamber in communication with the inner lend of said gun bore, and a wall contiguous to the inner end `of said bore; a projectile in said gun bore, said projectile having an inner end tace disposed in such relation to said wall that the building up of gas pressure adjacent the inner end tace of lthe-projectile will be retarded; and means for causing explosion of a nring `charge disposed in said tiring charge chamber.

5. In a perforating means of the character de` scribed, the combination of: a body having a gun bore: means for applying propelling gas pressure to the inner end of said gun bore, said means comprising a firing charge chamber in communication with the inner end'of said gun bore, and a wall contiguous to the innerend of said-bore; a ,"projectile in said gun bore, said projectile having an inner end face -disposed in such relation to said wall that the building up of gas pressure adjacent the inner end face of the projectile will be retarded; a ilring charge -in said firing charge chamber, said fixing charge occupying such portion of said ilring charge chamber that there will be left in said ring charge chamber a space of` such size as to provide a cushion to absorb vthe initial force of the explosion and serve as an accumulator for gas under pressure prior to the Y discharge of said projectile from said gun bore; and means for causing explosion of said ring charge.

6. In a perforating means of the character described, the combination of: a4 body having a gun bore; means for applying propelling gas pressure to the inner end of said gun bore, said means comprising a ilring charge chamber in communication with the inner end of said gun bore. and a wall contiguous to the inner-end o! said bore; a projectile in said gun bore: meanssure to the inner end of said gun bore, said means comprising chamber means to form an accumulator and a iiring charge chamber in communication with the inner end of said gun bore, and a wall contiguous to the inner end of said bore:

-a projectile in said gun bore; means operating to delay the discharge of said projectile from said gun bore: and means for causing explosion of a ring chargein said ring charge chamber.

8. In a perforating gunof the character described, the combination of: a body having a VV, pluralityof gun bores extending inward from the outer i'ace'thereof, with Ithe inner ends of said bores in communication; means for applying propelling gas pressure to the inner endsof said gun bores; and a plurality of projectiles one each of t plurality of gun bores extending inward from tlie outer face thereof, with thev inner ends of saidbores in communication; walls forming a firing charge chamber having communication with the inner ends of said gun bores; a plurality of projectiles one each of which is in one of said gun bores, the inner ends of said projectilesv being `spaced so close together as to retard the building up of pressure adjacent the inner end faces of said projectiles; a tiring charge in said firing charge chamber; and means for igniting said ri ing charge.

v10. In a perforating means of the character described, the combination of a projectile; Walls forming a gun bore to receive said projectile; and means; for applying a propelling gas .to the rear endof said gun bore, said means including a ring charge chamber in which a firing charge may be burned, said ring chargechamber being so formed relative to the inner end of said gun bore that the initial pressure of gas resulting from the burning of said firing charge will beapplied to a side of said projectile in said gun bore, thereby delaying movement of said projectile from its initial position in said gun bore.

11. In a perfor-ating means of the character described, the combination of: a projectile; walls forming a gun bore to receive said projectile; and means for applying a propelling gas to the rear end of said gun bore, said means including a ring charge chamber in which a ring charge may be burned, said firing charge chamber being offset to a side of said gun bore and being connected to said gun bore by passage means so .placed that the force from the burning of a firing charge in said chamber will be directed against a side portion of said'projectilein said gun bore.

12. In a perforating means of the character described, the combination of walls forming a gun bore; means for applying a propelling gas pressure to the inner portion of said gun bore, said means comprising a portopening which communicates with one side of said gunbore; and a projectile positioned in said gun bore so that a portion of its rear end projects across said port opening for the purpose of receiving from a lateral direction the initial application of said gas pressure, to bind the projectile in the gun bore and delay its outward movement. y

13. in. a perforating means of the character described, the combination of: Walls forming a gun bore; a space communicating with the rear end ofv said gun bore; a projectile positioned in the gun bore so that a rear end portion of the projectile will extend into said space; delay means for said projectile comprising a wall engaging a portion of said rear end portion of said projectile so as to cover the same and leave a side portion of the projectile exposed; and means substantial- 1y instantaneously building up a propelling gas pressure in said space.

14. In a periorating means of the character described the combination of: walls forming la gun bore; a space communicating with the rear end of said gun bore; a projectile positioned in the gun bore so that a rear end portion of the projectile wiil extend into said space; delay means for said projectile comprising a wall placed so as to cover a side of said rear end portion and leave the opposite side thereof exposed; and meansvsubstantially instantaneously building up a propelling gasV pressure in said space.

15. A well casingv perforating gun comprising: means dening a gun bore; a bullettting the gun bore; means for generating an explosive pressure; means for diverting a limited portion 'of the explosive pressure to propel the bullet into positionfor full application of said explosive pressure during an initial period calculated to permit generation of. the explosive pressure to a high value.

16. A Well casing perforator, comprising: a gun body having a gun bore adapted to receive a bullet, and means for applying gas pressure into the gun bore at the side thereof; a bullet fitting the gun bore and positioned initially to close the gun bore to said gas pressure; and means'for introducing a portion only of said gas pressure behind the bullet to move the bullet'orwardly until the bullet opens said gun bore to the full gas pressure.

17. In a ,perforating gun, the combination of: a gun body having a gun bore adapted to receive a bullet, means for generating an explosive pressure, a port for introducing explosive pressure to the side of the gun bore, and means for diverting alimited portion of the explosive pressure to the rear of said gun bore; and a bullet tting said gun bore and initially closing said port, said bullet being propelled initially at a comparatively low velocity under urge of the limited portion of the explosive pressure, and upon uncovering said port at a high velocity under urge of the entire explosive pressure.

18. A well casing perforating gun comprising:-

a gun bodyhaving a gun bore and a. bullet'iitting said bore; means for applying explosive pressure to said bore; and means for diverting a limited portion only of the explosive pressure against the bullet to urge it forward in the gun bore for a predetermined interval before exposing the bullet to the entire explosive pressure.

19. A well perforating gun comprising: 'a gun body defining a gun bore, a cartridge chamber and a passage connecting the cartridge chamber to the side of the gun bore; an explosive cartridge in the cartridge chamber; a bullet in the gun bore, the bullet positioned to separate the pas sage from the gun bore; and means providing restricted communication between the cartridge chamber and the base end of said bullet where= by, upon ignition of said cartridge, initial more ment of the bullet along the gun barrel is im= peded to permit rise of pressure in said cartridge chamber before the bullet uncovers said passage and receives the full application of said explosive pressure.

20. A Well periorating gun comprising: a gun body defining a gun bore, a cartridge chamber, and a connecting passage extending laterally from the gun bore to the cartridge chamber; an explosive cartridge in said chamber; a bullet positioned in said gun bore to closesaid passage; the bullet and gun bore dening a restricted means of communication between the passage and the base end of the bullet to prevent full exposure to the pressures generated in the cartridge until the bullet uncovers said passage.

21. A well perforating gun comprising: a gun body deiimng a gun bore, a cartridge chamber and a passage extending from the cartridge chamber to a point in the side of but adjacent the inner end of the gun bore; an explosive cartridge for said cartridge chamber; a bullet for said gun bore initially iltting against the inner end of the gun bore to restrict communication between the passage and the base end of said bullet until the bullet is moved away from the inner end of the gun bore.

22. A gun perforator comprising: a gun body deilning a gun` bore, a cartridge chamber and a passage extending from the cartridge chamber and intersecting the gun bore adjacent its inner end; an explosive cartridge for said cartridge chamber; a bullet for said. gun bore, said bullet conforming tothe inner end of the gun bore and initially positionedthereagainst, and, when so positioned forming a slide valve substantially closing communication between the passagegand the gun' bore, there being suillcient clearance between the bullet and gun bore to permit a limited portion of the explosive pressure generated by ignition of said cartridge `to leak behindsthe bullet and 'propel the bullet ,forwardly at low velocity until it uncovers said passage thereby to introduce a time delay period between ignition of the explosive cartridge and full application of the resulting pressure on the bullet.

23. A well perforating gun comprising: a gun body having a gun bore, an explosive chamber, and a port connecting the chamber with the t side of the gun bore; a bullet positioned in the gun bore and closing said port; means sealing' the bullet from contact with the liquids in which the gun body may be immersed, said means being yieldable to the pressures of said liquids to hold said bullet against the inner end of said gun bore; and means for bypassing a limited portion of the pressure generated upon ignition of said lcartridge, and directing the bypassed pressure against the base of the bullet to urge the bullet along the gun barrel in opposition to'said liquid .A pressure until said ,bullet uncovers said port and is thereby exposed to the entire explosive pressure.

24, A method of imparting high acceleration to a bullet, characterized by: applying explosive pressure laterally into a gun bore through a. port located forwardly of the inner end thereof", placing the bullet in anl initial position at least partially closing communication between the gun bore and port to limit the effective application of pressure on the bullet until the bullet has moved forwardly' and uncovered the port, thereby to introduce adelay between ignition of an explosive charge and full application of its 'pressure against the bullet.

25. A -method of operating a gun perforator to obtain high muzzle velocityof the gun perforator bullet, characterized by: generating.an explosive pressure, diverting while generating the explosive pressure, a limited portion of the pressure, propelling a bullet by the diverted portion for a period calculatedA to. permit generation of the explosive pressure to a high value, then pro- :selling the lbullet by the fully generated force of said explosive pressure. n

26. A method of imparting high acceleration to a bullet, characterized by: generating an explosive pressure by the burning of an explosive charge; diverting a predetermined limited portion of said explosive pressure to a bullet during e the burning of the explosive charge, to move the bullet slowlyv from an initial position substantially unaffected by the explosive charge to a secondary position exposed to the full force of said explosive charge.

IRA`J. MCCULLOUGH. 

